Economic reduced-loss linear 12 - 13.8V / 2 - 25A power supply built with standard components.

The circuit features low impedance and good stability by using a TL431 reference and a classic 
2-transistor OP-AMP circuit.

The total cost of components of this circuit s about EUR10 / USD10 (Q1/2013), plus heat sink,
housing, and transformer. Board size is about 1/4 eurocard = 3.1" x 2.35". Share with friends!

The circuit is designed to work with off the shelf standard halogen lamp transformers and as
an option a thermistor/fan combo like the ones used in PC power supplies.

The board design uses polygons. After opening the .brd file, first use the DRC command with the
file 'besupreme.DRC', and then the 'ratsnest' command.

The board can be made single-sided with only the bottom layer, however for even better immunity
against high energy rf fields, a top layer is provided.

Components B1, Q4, and R14 should be installed on the heat sink under the circuit board before
soldering. The distance between drills for B1 and Q4 is 2.2" = 56mm.
A distance of 3/4" -1" / 20-25mm between print and heat sink is recommended.

This design can also be used for different output voltages, here are some examples.
24V (20-30V): R3=2k2, R13=9k1, C1-C2 40V.
6V (5-7.5V): R1=0, R2 open, R3=330, R4=150, R8=0, Q4 logic level. 

For maximum currents different to 20A, recalculate the value of C1, C2, R16 to R19. Limits to
Q4 change accordingly. For max currents above 5A, the high current paths designated by gaps in
the solder stop must be reinforced on the board by soldering additional copper wires to the traces.

2013 besupreme.de - share and improve! License under http://creativecommons.org/licenses/by-sa/2.0/